While I have no definitive data (I'm sure Marck does though), but I think there are some other minute differences depending on years/drivetrain. For instance there's probably a good 50# difference between a iron diff/leaf spring in the pre-81 years and the 81-82 aluminum diff/fiberglass spring. Plus, some of the earlier years, not sure where the cut off is, the 4-speed was an iron case versus later models with the aluminum case. In the grand scheme of things, these differences probably equate to less than a 1% difference. But if you're worried about such things, maybe you want to take that into consideration.